Far-infrared reflection study on crystal structures and dielectric properties of Ba(Mg1/3Ta2/3)O3-BaWO4 ceramics

Ba(Mg1/3Ta2/3)O-3-BaWO4 (BMT-BW) ceramics were synthesized at 1,490 degrees C for 3 h using the conventional solid-state sintering technique, with BW contents of 2, 4 and 6 wt%. Crystal structures were elucidated by X-ray diffraction (XRD), and vibration modes were obtained by far-infrared spectroscopy (FIR). Correlations among crystal structures, dielectric properties and phonon modes of the ceramics were evaluated. The results demonstrate that the lattice parameter ratio (c/a) and the ordering degree reach a maximum value at x = 0.04. Studies about the FIR spectra also show that the IR active modes near 230 and 540 cm(-1) reach a maximum value at x = 0.04. IR active modes near 360 cm(-1) split and new phonon modes appear at x >= 0.04, which agrees with the change in the crystal structures as proved in the XRD results. The correlations between dielectric properties and IR phonon modes were established with vibration modes as the media.